1. Field of the Invention
This invention generally relates to braking systems for vehicles. More particularly, this invention relates to a control system for automatically applying and xe2x80x9clockingxe2x80x9d a vehicle brake in an applied condition during times when it is not safe for the vehicle to move. The invention may be adapted for use with brakes of various types, for example, air parking brakes or mechanical parking brakes, or by adapting a hydraulic xe2x80x9capplicationxe2x80x9d brake, an air xe2x80x9capplicationxe2x80x9d brake, or an electric brake to serve as a parking brake. The automatic application and locking of a vehicle brake may be actuated by signals from various sensors/switches inside and outside the vehicle.
2. Related Art
Commercial and public transportation vehicles typically utilize the following types of conventional brakes:
1) Air parking brakes utilize an air-controlled spring system that cooperates with the brake shoes of a vehicle""s back wheels. Air parking brake systems exist in commonly-used commercial vehicles, such as trucks, commercial buses, or school buses. The air parking brake system comprises an air source, the spring mechanism, and an air control valve called an xe2x80x9cair loading valvexe2x80x9d between the air source and the spring mechanism. The air loading valve is controlled only by a manual handle, which is in the vehicle cab on the dashboard or in other positions accessible to the operator. The loading valve manual handle works in a xe2x80x9cPull To Applyxe2x80x9d and xe2x80x9cPush To Releasexe2x80x9d manner. Pulling the handle closes the air loading valve, whereby air pressure from the air source is blocked and downstream air pressure is vented so that the springs move to a position that applies the brake. Pushing the handle opens the air loading valve and closes the vent, whereby air is supplied to the spring mechanism so that the springs move to a position that releases the brake.
2) Air application brakes, sometimes called xe2x80x9cfoundation brakes,xe2x80x9d are the conventional means, in vehicles with air brakes, to slow and stop the vehicle, for example, during normal xe2x80x9cstop and goxe2x80x9d driving. The xe2x80x9cair application brakesxe2x80x9d are operated by a foot-actuated air control valve, which allows incremental application of the brakes depending on how far the operator has pushed on the foot pedal.
3) Mechanical parking brakes utilize a mechanical linkage or a cable, to operatively connect a manual handle in the vehicle cab either to brake shoes at the rear wheels, or to external brake bands or internal brake shoes working with a brake drum mounted on the drive line. The manual handle is typically either a pull-on hand-operated handle, or a push-on foot-operated pedal.
4) Hydraulic xe2x80x9capplicationxe2x80x9d (or xe2x80x9cfoundationxe2x80x9d) brakes are the conventional means, in vehicles with mechanical parking brakes, to slow and stop the vehicle during normal driving. A hydraulic application brake system typically comprises a master brake cylinder for applying hydraulic force to brake shoes at the wheels, and a manual foot-pedal for actuating the master cylinder. Pushing on the brake pedal causes the brake cylinder to increase the fluid pressure in the line to the brake shoes at the wheel, which inhibits the rotation of the wheel to a incremental amount depending on how far the operator has pushed on the brake pedal. When the pedal is released, the master cylinder retracts to reduce or eliminate the pressure in the brake line, disengaging the brake shoe pads from contact with the brake drum and thereby allowing unhindered rotation of the wheel. Hydraulic application brakes are used in most family cars, sport utility vehicles, pick-ups, vans, and larger vehicles such as some school buses.
Regarding Vehicle Movement during Unsafe Conditions
Conditions may exist in or around a vehicle that make it unsafe for the vehicle to be in motion. Conventional safeguards against vehicle movement when such a condition exists are inadequate, at least in part because the safeguards typically depend on the driver taking appropriate action. This invention, without requiring driver action or involvement, automatically detects such conditions and automatically applies or locks the brakes, thereby preventing potentially unsafe vehicle movement.
Vehicle movement when conditions exist that potentially make such movement unsafe are generally the result of (1) the driver""s failure to properly apply or engage the parking brake or application/foundation brake system, (2) a third party""s intentional release or interference with the parking brake, or (3) the driver""s failure, whether intentional or inadvertent, to detect and/or react to conditions which may make vehicle movement unsafe.
Examples of potentially dangerous conditions where movement of a vehicle may be unsafe include but are not limited to the following:
A driver leaves a vehicle, or is otherwise not in a position to safely operate the vehicle and fails to properly set the parking brake.
A driver attempts to put a vehicle in motion when people are attempting to enter or leaving the vehicle.
A driver attempts to put a vehicle in motion with a door open, wheel chair ramp in use, luggage compartment unlatched, or other equipment similarly not in a safe operating mode.
A driver puts a vehicle in motion when an object is in close proximity creating the potential for a collision. Examples include a driver failing to notice a pedestrian stepping in front of a bus or a child playing behind a parked car.
A driver""s ability to recognize the existence of an unsafe condition is impaired. Examples include radio noise masking the warning whistle of a train at a railroad crossing, a driver who is intoxicated, or a passenger who has not fastened safety restraints.
A vehicle that is approaching too close to an object, such as a truck backing up to a loading platform.
A vehicle with equipment that has failed or is not within acceptable safety ranges, such as loss of tire or oil pressure.
An unauthorized driver is attempting to move or steal the vehicle.
Patent Literature
There are instances of parking brake locking systems in the patent literature, but none are as effective and safe as that of the present invention. None of the prior art locking systems includes the comprehensive safety features of the present invention.
There are inventions for the automatic engagement of parking brakes upon the turning off of an ignition or engine key switch. U.S. Pat. No. 5,624,352 (Smale) discloses an xe2x80x9cignition-controlled parking brake interlock.xe2x80x9d This lever and latch interlock invention is activated by turning off the vehicle ignition key. U.S. Pat. No. 5,675,190 (Morita) discloses an xe2x80x9coperating apparatus for parking brake and method for releasing parking brake.xe2x80x9d The Morita invention uses a combination of the vehicle ignition key switch, with ON-OFF positions, and a three-way parking brake switch with ON-OFF-RESET positions, to engage the parking brake. A drawback of the Morita invention is the complexity incumbent in the use of its multiple switches.
U.S. Pat. No. 4,519,653, issued to Smith, discloses an anti-theft lock device, which includes a solenoid for attachment to the outer end of a conventional loading valve. When de-energized, the solenoid moves a lock member into the path of the valve actuating member of the conventional loading valve, physically blocking the actuating member so that it cannot be pushed in to disengage the parking brake. If the conventional loading valve has been disengaged prior to de-energizing of the solenoid, then the solenoid and its lock member are ineffectual, in that the lock member merely slideably contacts the side of the valve actuating member in a non-interfering relationship, and, hence, does not apply the brake or have any effect on the brake. Thus, the Smith device may be used as an anti-theft device, after the driver has manually pulled on the brake and turned off the ignition, but it does not have the automatic emergency safety features of the present invention.
Brooks, U.S. Pat. No. 5,553,795, illustrates a safety system with seat and door control. Brooks includes circuitry that places a weight-sensor switch in the driver""s seat assembly parallel with door switch circuitry. This way, if the driver is absent from his/her seat and the door is open, the circuit is opened and a solenoid in the air line to the brakes closes. If the driver is in his/her seat, the circuit stays closed even if the door is open, or, if the door is shut, the circuit stays closed even if the driver is out of the seat.
Green, UK Patent Application GB 2 265 679, discloses an apparatus which has a multiple-position switch, which, in a first position, de-energizes a solenoid valve to block air to the brakes, and, in a second position, also cuts off electricity to the engine starting system and cuts off fuel supply to the engine.
Therefore, some inventions exist for the control of brakes for safety and theft-deterrence, but there is still a need for a versatile, reliable system that is compatible with various types of existing brake technology. There is still a need for a comprehensive automatic brake control system to prevent vehicle movement during potentially unsafe conditions at various stations inside, outside, or around the vehicle, and to better inform the vehicle operator of the potentially unsafe conditions. There is a need for a control system that automatically applies a brake and xe2x80x9clocksxe2x80x9d it in the xe2x80x9conxe2x80x9d condition throughout the duration of potentially unsafe situations, and that also prevents automatic setting of the brake while the vehicle is traveling. There is a need for such a control system that does not require driver action or involvement, but that does allow an authorized driver to override the automatic systems under some circumstances. The present invention meets these needs.
The present invention is a brake control system that automatically detects potentially unsafe conditions and then enhances safety by automatically applying a brake and maintaining the brake in the applied position (xe2x80x9clocking the brakexe2x80x9d) and/or by controlling other equipment. An object of the present invention is to provide an automatic control system that requires little driver action or involvement. An object of the invention is to enable sensors to detect the potentially unsafe conditions in or around the vehicle, to automatically alert the driver to the existence of such conditions through visual and or audio or other means, and, when appropriate, to automatically control the brakes and/or other equipment. Potentially dangerous conditions may include, for example: 1) equipment-related conditions such as a driver exiting the vehicle without applying the parking brake or without turning off the vehicle; operating a disabled person""s lift; passengers entering and exiting the vehicle; engine or other vehicle malfunctions detected by diagnostic sensors; or a driver being distracted by radios, cell-phones, or monitor screens; or 2) undesirable- or dangerous-driver-related conditions such as a driver failing a breath alcohol test or an identity test. Other objects of the invented control system may include preventing the brake from being automatically set while the vehicle is moving, and allowing a driver to override the automatic control system during some circumstances.
As a result of these and other objects of the invention, the invented system allows a vehicle operator to focus more on safe driving and vehicle operation, whether traveling or parked, and on the surrounding conditions, rather than on repeated manual operation of the parking brake, and repeated checking of the parking brake handle position. With fewer distractions, and fewer responsibilities for accidental misuse or release of the parking brake, the vehicle operator can perform his/her job more safely. Further, elimination of the frequent pulling and pushing of the parking brake manual handle may reduce carpal tunnel syndrome in veteran drivers.
The invented control system comprises a xe2x80x9cmanagement mechanismxe2x80x9d for applying a brake, a controller with the logic that decides when the brake should be applied and that electronically actuates the management system to apply the brake, and various circuits and sensors for linking the controller to the various stations inside, outside, and around the vehicle. The invented controller may be used with a variety of existing brake systems, by adapting the management mechanism for the particular type of brake system being used.
In vehicles containing an air parking brake, the invented controller preferably controls a vented solenoid valve that replaces the conventional loading valve in the air line to the spring mechanism.
In vehicles containing a hydraulic application brake system and a mechanical parking brake (either wheel brakes or drive line brakes), the invented control system may be adapted for either the hydraulic application brake system or the mechanical parking brake. When adapted for the hydraulic application brake system, the invented management mechanism may be of two general types: 1) an air, hydraulic-oil, spring, or other actuator that causes the master cylinder to apply the brake; or 2) a pressure generator that is xe2x80x9cinsertedxe2x80x9d between the master cylinder and the brake mechanism and that creates pressure in the brake fluid line to apply the brake. After either type of management system is installed in a hydraulic brake system, the adapted brake system then serves double duty as a xe2x80x9chydraulic parking brakexe2x80x9d as well as a hydraulic application brake.
When adapted for the mechanical parking brake system, the invented management mechanism operatively connects to the mechanical brake linkage, such as a brake cable. The management mechanism may be, for example, apparatus for air-actuation, hydraulic-oil actuation, spring-actuation or electric-actuation of the mechanical brake linkage.
The various circuits, sensors, and switches included in the invented control system automatically 1) sense conditions, of one or more xe2x80x9cstationsxe2x80x9d in or around the vehicle, that are potentially dangerous if the vehicle moves and 2) automatically signal the controller, which decides whether or not to xe2x80x9ctripxe2x80x9d the management mechanism to apply the brakes. Such xe2x80x9cstationsxe2x80x9d may be vehicle components, such as the ignition system, the vehicle main door and/or an emergency door, a wheelchair lift, a dump truck bed, a delivery vehicle door, a trailer, a crane boom, outrigger, seat belts, a pressure-sensing operator""s seat sensor, tire pressure sensor, engine oil pressure sensor, emissions sensor, air bag sensor, or other vehicle or engine diagnostic sensors that sense and signal the controller when conditions are outside of the normal operating range. Other xe2x80x9cstationsxe2x80x9d may include equipment, objects, or location of people outside a vehicle, for example, that are positioned too near or moving too near to the vehicle in a street, parking lot, loading dock or warehouse. Other xe2x80x9cstationsxe2x80x9d may include test units for driver condition or desirability, such as a breath analyzer, a voice analyzer, or an access-code key-pad, for example.
In general, signals from the various xe2x80x9cstationsxe2x80x9d inside, outside, or around the vehicle to the controller are created by sensors or switches being actuated by the movement of, or the position of, equipment or people, and this actuation signaling the controller, for example, via sensor circuits or other electric or electronic means or other transmission. In some cases, actuation of the sensor or switch at a particular station comprises interruption, either the positive side or the negative/ground side, of the controller circuit including the particular sensor or switch. Various means of switching/sensing may be used, for example, conventional electrical contact, sound-switching, light-emitting-switching, magnetic-switching, fluid, pressure, radar, sonar, microwave, or any other conceivable switching or sensing. When a sensor or switch, or, alternatively, when a certain combination of sensors or switches, is actuated, and the controller decides that conditions are appropriate, the controller xe2x80x9ctripsxe2x80x9d the management mechanism and the management mechanism applies the brakes. As long as the condition causing the xe2x80x9ctripxe2x80x9d persists, the brakes remain locked in the applied condition in most circumstances. For example, a switch may be operatively connected to a handicapped lift system, and the switch may be electrically/electronically connected to the invented controller, so that using the lift opens a circuit to the controller, which trips the management mechanism to apply and lock the brakes. Once the lift system is not is use, the driver may release the brake. Likewise, a switch may be operatively connected to a door, and the door switch may be electrically/electronically connected to the invented controller, so that opening the door breaks its sensor circuit and trips the management mechanism to apply and lock the brakes. Once the door is closed, the driver may release the brakes. For simplicity hereafter and in the claims, the term xe2x80x9csensorxe2x80x9d may be used to indicate any sensor or switch at a xe2x80x9cstationxe2x80x9d that is actuated by conditions at the station to signal the controller.
A feature of the preferred invented control system is that loss of power to the management mechanism causes it to apply and lock the brake. In the especially-preferred embodiments, any time that power is removed from the control module (the xe2x80x9ccontrollerxe2x80x9d), power is also removed from the management mechanism and the brakes are applied. The positive power input for the preferred controller is activated by either direct or indirect operation of the ignition switch of the vehicle. Therefore, turning the vehicle ignition to the xe2x80x9cOFFxe2x80x9d position de-activates the controller and the management mechanism to apply the brakes.
The preferred brake control system also includes a sensor and logic for preventing automatic application of the brake if the vehicle is in motion above a certain speed. This feature of the invented control system may be adapted to interface and cooperate with various designs of speedometers, such as magnetic, electrical, or electronic sensor types, or other means for measuring vehicle motion or speed. For example, a conventional speedometer magnetic pick-up may be used to signal the controller for this purpose.
The preferred brake control system also includes features that improve operability in substantially all vehicles, specifically, a signal qualifying circuit and noise suppression functions. The preferred signal qualifying circuit detects the presence of a constant voltage maintained for a minimum duration of time, in order to verify that a signal to the controller is xe2x80x9creal,xe2x80x9d that is, it is not a signal created by a jiggling of a switch, electric noise or other false signals. Alternatively, a qualifying circuit may also use other measurements, such as frequency, to verify true signals. The noise suppression functions may be affected by a combination of various transient suppression inductors, capacitors, diode and surge protectors.
The preferred brake control system includes a manual brake-releasing override system to override the controller""s application of the brakes, during emergencies and/or at the driver""s discretion. For example, if the invented controller applies and locks the brakes when the vehicle is still in traffic, the driver may use the manual brake-releasing override to release the brake for enough time to move the vehicle to the side of the road. The manual brake-releasing override may include, for example, the driver pushing with a finger on a portion of the spool (SP) of the air valve to temporarily allow air through to the spring to temporarily release the brake. Alternatively, the manual brake-releasing override may be assisted mechanically or electrically.